In standard mechanically switched capacitor banks and harmonic filters, typical discharge periods of 5-10 minutes limit how quickly capacitors can be re-energised. Dynamic Point-On-Wave (P-O-W) technology negates the requirement for discharge periods enabling immediate re-energisation of capacitors that is governed only by the reclosure speed of the mechanical switch or circuit breaker being used.
Enspec has successfully commissioned a fast-switched 20kV C-Type harmonic filter under SynchroTeq control on a wind farm in Ireland. Acting as a Zero Voltage Crossing (ZVC) switching device, it synchronises with the voltage waveform and through knowledge of the circuit breaker operation time (Predicted Operating Time), ensures electrical conduction begins at the desired point where bus and capacitor voltages are equal.
It has also been shown that this switching strategy leads to operations free from transients and inrush currents. By employing this method of control a capacitor bank or harmonic filter can satisfy the repeat switching event criteria as specified by the latest UK Grid Code coming into effect December 2017 (5 switching events, 15s apart).
SynchroTeq is also widely deployed in the mitigation of transformer switching transients and inrush currents.
Tim Rastall MEng MIET